Nitric acid not condensing.
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Geo
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You are losing nitric acid to thermal decomposition. Nitric acid boils at 181°F. NO3 is colorless and produces nitric acid through distillation. NO2 has to be bubbled through water to produce nitric acid. If the reaction is too hot, the NO3 decomposes to NO2. What temp is the reaction when it's producing red NO2?
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Geo
Well-known member
My comment above was edited to add boiling point of nitric acid.
Potassium nitrate and sulfuric acid will produce nitric acid with no extra water producing nearly pure 98% white fuming nitric acid. The resulting solid cake left behind is potassium sulfate and is a real pain to remove from the boiling flask. It has to be dissolved with boiling water and potassium sulfate is mildly soluble in water.
Potassium nitrate and sulfuric acid will produce nitric acid with no extra water producing nearly pure 98% white fuming nitric acid. The resulting solid cake left behind is potassium sulfate and is a real pain to remove from the boiling flask. It has to be dissolved with boiling water and potassium sulfate is mildly soluble in water.
Dilute nitric acid will dissolve more metals into the solution.
The more added water or the more dilute your acid is, the more metals it will dissolve and the less of your acid will be wasted forming gases that escape the reaction.
The water will not only hold more dissolved nitrate salts, but the water will hold or dissolve the red NO2 gases from the reaction (the water basically reforms nitric acid by absorbing and reacting with the NO2 gas).
Dilution can also help to slow down the reactions which can also help it to run cooler with less heat generated the gases stay in solution longer (to react if they are able to.
The clear NO portion of the NOx gas is not water-soluble and would be lost in this more dilute reaction.
Yes, it is a two-edged sword, the more diluted the slower the reaction will be.
As normal, it is good policy to use heat and concentration towards the end of the reaction when it slows towards a stop to drive the reactions to completion, to get full use of our nitric on metals like silver...
Adding some oxygen in the form of hydrogen peroxide (3% which is mostly water anyway would be fine) can help to make the nitric acid go further as the oxygen in the solution reacts with the clear NO gas to form red NO2 gas which is water-soluble and basically makes more nitric acid in solution from the water and hydronium ions in solution which can dissolve more silver or whatever metals your making or converting into soluble nitrate salts which dissolve in the acidic water of the solution
The more added water or the more dilute your acid is, the more metals it will dissolve and the less of your acid will be wasted forming gases that escape the reaction.
The water will not only hold more dissolved nitrate salts, but the water will hold or dissolve the red NO2 gases from the reaction (the water basically reforms nitric acid by absorbing and reacting with the NO2 gas).
Dilution can also help to slow down the reactions which can also help it to run cooler with less heat generated the gases stay in solution longer (to react if they are able to.
The clear NO portion of the NOx gas is not water-soluble and would be lost in this more dilute reaction.
Yes, it is a two-edged sword, the more diluted the slower the reaction will be.
As normal, it is good policy to use heat and concentration towards the end of the reaction when it slows towards a stop to drive the reactions to completion, to get full use of our nitric on metals like silver...
Adding some oxygen in the form of hydrogen peroxide (3% which is mostly water anyway would be fine) can help to make the nitric acid go further as the oxygen in the solution reacts with the clear NO gas to form red NO2 gas which is water-soluble and basically makes more nitric acid in solution from the water and hydronium ions in solution which can dissolve more silver or whatever metals your making or converting into soluble nitrate salts which dissolve in the acidic water of the solution
Ok so If I use the recipe I have
80g potassium nitrate
60ml sulfuric 90%
If I was to add 40ml of water to the boiling flask it should distill at about 60-65 % if I’m understanding what you said correctly?
I watch the Doug’s lab videos that someone mentioned he is using a different salt and I will be looking for those as it looks to be a lot better as you don’t have the solid mass to deal with after completing. But right now I have about 10 lbs of potassium nitrate to use.
80g potassium nitrate
60ml sulfuric 90%
If I was to add 40ml of water to the boiling flask it should distill at about 60-65 % if I’m understanding what you said correctly?
I watch the Doug’s lab videos that someone mentioned he is using a different salt and I will be looking for those as it looks to be a lot better as you don’t have the solid mass to deal with after completing. But right now I have about 10 lbs of potassium nitrate to use.
Jimbriese,
Look into making poor man's nitric acid solution, it can be used as-is on many base metals or reactions where some sulfate will not cause problems with the reactions.
Poor mans nitric which is a good recipe for the reaction to get 68% HNO3 which can then be distilled for use with silver or for making aqua regia, by making poor-mans nitric acid and freezing the solution which helps you to remove the bulk of sulfate salts (that become a problem during the distilling process) is very helpful before trying to distill the solution, by removing the bulk of sulfate salts that form from the reaction before distilling the solution will put you much further ahead as you will not have many of the insoluble salts to deal with during the distillation process.
I prefer sodium nitrate salts over potassium nitrate salts their solubility makes it easier to deal with their sulfate compounds when making nitric acid.
Before attempting to distill, spend time understanding how to perform it safely, simple things like lowering the temperature on a reaction can cause a vacuum in a pressurized vessel, this vacuum can suck back cold liquid into the boiling hot glass flask of hot acids, shattering the glass and splashing and spraying hot acids all over you, and your laboratory...
Look into making poor man's nitric acid solution, it can be used as-is on many base metals or reactions where some sulfate will not cause problems with the reactions.
Poor mans nitric which is a good recipe for the reaction to get 68% HNO3 which can then be distilled for use with silver or for making aqua regia, by making poor-mans nitric acid and freezing the solution which helps you to remove the bulk of sulfate salts (that become a problem during the distilling process) is very helpful before trying to distill the solution, by removing the bulk of sulfate salts that form from the reaction before distilling the solution will put you much further ahead as you will not have many of the insoluble salts to deal with during the distillation process.
I prefer sodium nitrate salts over potassium nitrate salts their solubility makes it easier to deal with their sulfate compounds when making nitric acid.
Before attempting to distill, spend time understanding how to perform it safely, simple things like lowering the temperature on a reaction can cause a vacuum in a pressurized vessel, this vacuum can suck back cold liquid into the boiling hot glass flask of hot acids, shattering the glass and splashing and spraying hot acids all over you, and your laboratory...
Butcher is right. I know because I learned those exact methods from him several years ago to make nitric acid. I still use them pretty often even now when I need nitric and run out. With some care it can be used on some metals by just mixing the right amounts in hot water with your metal. It seems an enormous task when first starting out but will get easier with time and study.
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My standard operating procedure for nitric:
1L round-bottom flask
340g NaNO3 sodium nitrate prills
200g H2O
210g H2SO4 concentrated sulfuric acid
Add powder funnel to round bottom flask. Place flask in ring on scale. Add one quartz boiling chip to flask, note mass, and tare scale. Add prills first, liquid, and then sulfuric. Immediately transfer round bottom to heating mantle and seal glassware. Dial in heating mantle for 118C vapor temperature. Add aluminum foil reflectors around flask and thermometer adapter. Liquid should come over clear. Boil until bubbles get small, usually under an hour. Do NOT leave it unattended.
Let cool to 80C, carefully add 10mL of cold water to the boiling flask to keep the salts from crystallizing. Pour out sodium hydrogen sulfate leftovers before they cool (and solidify).
Yield: about 250mL of about 40-50% nitric acid (a perfect concentration for dissolving silver or base metals).
Hazards: without sufficient water in the flask, red Nitrogen Dioxide fumes will be emitted during distillation. These are POISONOUS: the nitrogen dioxide LC50 for inhalation is below 200ppm, more toxic than cyanide gas. (You can die up to several weeks later, the gas having burned the inside of your lungs.) SEVERE FIRE HAZARD: hot nitrogen dioxide gas will cause rubber O-rings to emit flames and smoke.
Hazard mitigation: Work in a fume hood with negative pressure. Use secondary containment, since none of these materials are OK to spill on anything except glass. Stop heating while there is still visible liquid in the boiling flask. Do not allow the vapor temperature to exceed 130C. If red gas is escaping apparatus, vacate the area immediately and turn off heating remotely.
1L round-bottom flask
340g NaNO3 sodium nitrate prills
200g H2O
210g H2SO4 concentrated sulfuric acid
Add powder funnel to round bottom flask. Place flask in ring on scale. Add one quartz boiling chip to flask, note mass, and tare scale. Add prills first, liquid, and then sulfuric. Immediately transfer round bottom to heating mantle and seal glassware. Dial in heating mantle for 118C vapor temperature. Add aluminum foil reflectors around flask and thermometer adapter. Liquid should come over clear. Boil until bubbles get small, usually under an hour. Do NOT leave it unattended.
Let cool to 80C, carefully add 10mL of cold water to the boiling flask to keep the salts from crystallizing. Pour out sodium hydrogen sulfate leftovers before they cool (and solidify).
Yield: about 250mL of about 40-50% nitric acid (a perfect concentration for dissolving silver or base metals).
Hazards: without sufficient water in the flask, red Nitrogen Dioxide fumes will be emitted during distillation. These are POISONOUS: the nitrogen dioxide LC50 for inhalation is below 200ppm, more toxic than cyanide gas. (You can die up to several weeks later, the gas having burned the inside of your lungs.) SEVERE FIRE HAZARD: hot nitrogen dioxide gas will cause rubber O-rings to emit flames and smoke.
Hazard mitigation: Work in a fume hood with negative pressure. Use secondary containment, since none of these materials are OK to spill on anything except glass. Stop heating while there is still visible liquid in the boiling flask. Do not allow the vapor temperature to exceed 130C. If red gas is escaping apparatus, vacate the area immediately and turn off heating remotely.
Geo
Well-known member
Calcium nitrate, water and sulfuric acid produces nitric acid at 68% right from the reaction. The resulting cake will be calcium sulfate (gypsum) and is much easier to remove from your glassware. I can get the amounts and temp. It's in my notes. I'll have to dig it out.
